An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are either destroyed during reentry or discarded in space. ELVs typically consist of several rocket stages that are discarded sequentially as their fuel is exhausted and the vehicle gains altitude and speed. As of October 2019, most satellites and human spacecraft are currently launched on ELVs. ELVs are simpler in design than reusable launch systems and therefore may have a lower production cost. Furthermore, an ELV can use its entire fuel supply to accelerate its payload, offering greater fuel efficiency. ELVs are proven technology in widespread use for many decades.[1] ELVs are usable only once, and therefore have a significantly higher per-launch cost than reusable vehicles. New reusable launch systems under development by private companies such as SpaceX and Blue Origin have the potential to obsolete many existing ELVs due to the lower per-launch costs of reusable rockets.[2]